A joint memoir by Anderson Cooper and Gloria Vanderbilt will be published in April, just days before the airing of an HBO documentary featuring the famous designer-socialite and her CNN anchor-son.

Harper, an imprint of HarperCollins Publishers, told The Associated Press on Thursday that it had acquired “The Rainbow Comes and Goes: A Mother and Son Talk About Life, Love, and Loss.” The book will be released April 5, four days before HBO airs “Nothing Left Unsaid,” which also screens later this month at the Sundance Film Festival. CNN will show the movie on April 30.

According to Harper, the book will feature “hilarious and always touching exchanges” between Cooper and Vanderbilt and will contrast Vanderbilt’s “unwavering optimism” with her son’s “darker outlook.”